In the preferred field of application of the invention, it is known to read the mold number carried by a bottle, for example for the purposes of associating defects detected by sensors with the number of the faulty mold, of automatically rejecting bottles manufactured using a faulty mold, and of automatically extracting bottles coming from one or more molds, in particular for sampling purposes. Another advantageous application for the subject matter of the invention lies in the field of sorting bottles, whether empty or full, by mold number.
In the state of the art, it is known to use a reader device placed on a bottle conveyor line. Given the random positioning of bottles on a conveyor line, it is necessary to turn each bottle about its vertical axis in front of the reader device so as to scan the entire periphery of the bottom margin of the bottle in order to read the relief corresponding to a mold number.
The major drawback with that technique lies in rotating each bottle. As a result, there is a risk of damaging the outside wall of the bottle because of the rotary drive mechanism rubbing there against. In addition, rotating bottles reduces inspection rate compared with other inspection operations that are performed straight through, i.e. without interfering with the process of moving the bottles in translation.
In an attempt to remedy the drawbacks of that technique, French patent application FR 2 747 211 proposes an opto-electronic reader device having a light source which illuminates all of the periphery of a portion of the body of the receptacle.
The light source is constituted by two elements disposed on either side of the conveyor, level with the bottom margin of the bottle. The device also has two frustoconical mirrors disposed on either side of the conveyor level with the body of the bottle and adapted to receive light reflected by the bottle and to transmit the light to a camera placed above the bottle. The camera is associated with an electronic processing system capable of reproducing a complete image of the zone of the bottle that includes the mold number.
Although such a relief reader device is designed to avoid any need for rotating bottles, it has to be understood that implementing such a device leads to the appearance of parasitic reflections that reduce image contrast, such that relief is buried in background noise making it difficult to read. In addition, implementing two mirrors on either side of the conveyor does not suffice to recover all of the beams reflected over the entire periphery of the bottle. To remedy that drawback, the above patent application proposes using four mirrors, thus requiring receptacles to be handled in a special manner and reducing the inspection rate.